The typical fluid pump has a pump body defining a pumping chamber with a suction port, plunger port, and discharge port. A suction valve is positioned in the suction port, a reciprocating plunger is positioned in the plunger port, and a discharge valve is positioned in the discharge port.
The suction valve is usually a spring-loaded check valve for allowing the flow of fluid from the low pressure side of the pump through the suction port into the pumping chamber while preventing the backflow of fluid through the suction port. The discharge valve is usually a spring-loaded check valve for allowing the flow of fluid from the pumping chamber through the discharge port to the high pressure side of the pump while preventing the backflow of fluid through the discharge port.
The typical spring-loaded check valve used in the suction and discharge ports of a fluid pump has a valve seat. The suction and discharge ports of a typical fluid pump are generally cylindrical openings into the pumping chamber. Thus, the valve seat has a generally cylindrical configuration with a central bore therethrough and is symmetrical about a central axis. The valve seat has a slightly tapered outer surface (male) which mates with a similarly slightly tapered inner surface (female) of the port to create an pressure-tight interference fit. Typically, the suction and discharge valves are vertically disposed in the pump, that is, the axis of the cylindrical valve seat is vertically oriented in the pump body, preferably such that the vertical axes of the valve seats of suction and discharge valves are co-axially aligned.
The typical valve seat has a frusto-conical shaped seat portion formed on one end thereof that is adapted to seat a flange portion on a valve element that reciprocates in the bore of the valve seat. The same end of the valve seat has exposed male threads formed thereon so that a cage having corresponding threads can be threaded onto the valve seat to capture a spring and valve element adjacent the valve seat. Thus, the valve element is spring-loaded in the valve seat in a normally closed position. When a fluid pressure differential across the check valve exerts a force on the valve element in a direction opposed to the closing force exerted by the spring and that is sufficient to overcome the spring, then the spring-loaded valve element moves against the spring to open the check valve and allow fluid therethrough. But if a fluid pressure differential across the check valve exerts a force on the valve element in the same direction as the closing force exerted by the spring, then the spring-loaded valve element is pressured more tightly closed. Thus, the check valve only allows fluid to flow therethrough in one direction.
The plunger of the pump is positioned to reciprocate back and forth in the plunger port. During the back stroke of the plunger, the increasing volume of the pumping chamber creates decreasing fluid pressure or suction in the chamber, which opens the suction valve in the suction port to draw fluid into the pumping chamber. During the forward stroke of the plunger, the decreasing volume of the pumping chamber creates increasing fluid pressure in the chamber, which closes the suction valve and opens the discharge valve in the discharge port to pump fluid through the discharge valve to the high pressure side of the pump.
During operation of the pump the valve seat becomes worn and must be periodically replaced due to the repeated reciprocation of the valve element and the fluid flow. Particularly when pumps are used for materials containing mud, sand, or other gritty or abrading materials, as in oil wells, the wear upon the walls of the valve seat about the valve element is so rapid as to speedily render the pumps unfit for service unless the surfaces are frequently renewed.
But during operation of the pump the hammering action of the spring-loaded valve element and the high pressures tends to wedge the valve seat in an extremely tight interference fit with the inner surface of the port in the pump body. Sometimes the valve seat becomes deformed and rusts in place. For these and additional reasons, the valve seat can become extremely difficult to remove. Thus, there are many prior art devices for pulling the valve seat from the pump body that attempt to solve this problem of removing the valve seat with varying degrees of success.
Typically, a valve seat removing tool is a tapered mandrel that receives a pair of jaws. The jaws have a complimentary, tapered central passageway and it is a common practice to hold the jaws biased inwardly with an O-ring or the like. The valve removing tool is run through the interior of the valve whereupon the jaw shoulders engage the bottom face of the valve seat and then the tool is set by moving the mandrel respective to the jaws. Hydraulic jacking or knocking devices are used to urge the tool away from the pump body and thereby force the worn valve seat from the pump body.
But occasionally the valve seat cannot be forced from the pump body, which causes a dilemma because the prior art removing tool has been firmly set in the valve and cannot be retrieved unless it brings the valve seat out of the pump body. Accordingly, expensive pump tear-down may be required in order to retrieve the captured valve seat removing tool and thereafter use other more expensive means of removing the valve seat from the pump.
For example, U.S. Pat. No. 3,990,139 issued Nov. 9, 1976 to Daniel Lee Touchet discloses a valve seat puller utilizing a plurality of J-shaped hooks mounted for limited pivotal movement on a hook support block. The hook support block and J-shaped hooks are supported by a threaded rod extending through a central aperture in the support block and secured in place by a lock nut. The J-shaped ends of the hooks are spread to engage the lower rim of the valve seat. The threaded rod passes through an aperture in a pump support plate spaced above the hook support block and is secured to the pump support plate by a drive nut. By applying rotary motion to the rod or the drive nut, the rotary motion will be translated into vertical axial motion of the rod, thus applying a lifting force to the hooks and valve seat to free the seat. But this device does not contemplate the problem of when the valve seat remains fully stuck despite all efforts to remove it, in which case this valve puller also becomes irretrievably stuck in the pump, thereby compounding the service problem.
U.S. Pat. No. 1,652,857 issued Dec. 31, 1927 to Edgar E. Greve discloses a device for removing valve seats. The device includes a cross-bar through the center of which is slidably passed the threaded upper end of a mandrel. Above the cross-bar on the threaded upper end of the mandrel is an operating nut by means of which the mandrel may be raised and lowered. The lower portion of the mandrel, below the threaded area thereof, is squared, and below the squared portion the mandrel is flared to provide oppositely inclined faces. Slidably fitted over the squared portion is a transverse adjusting bar having laterally projecting lugs to provide pivotal suspension of dogs. The inner faces of the dogs are constructed so as to provide large contacting surface with the inclined faces of the mandrel. The lower end of each of the dogs terminates in a lip or ledge. The under faces of the dogs are rounded and they are so balanced that they have a tendency to swing in toward each other when hanging free of the tapered faces of the mandrel. Once passed through the valve seat, the mandrel is lifted to move the dogs away from each other, forcing the ledges or lips under the valve seat. By turning the nut, the mandrel may be gradually raised to attempt to lift the valve seat. But typical of the problem with prior art devices, if the valve seat refuses to budge, there is no way to lift the tool without having the inclined faces of the mandrel force the dogs away from each other such that the ledges or lips engage the valve seat.
U.S. Pat. No. 1,650,023 issued Nov. 22, 1927 to Raymond F. Maxwell, discloses a tool for removing the liner for a pump. The liner removing tool has a ring-like threaded portion from which project opposite pairs of lugs. From each pair of lugs is pivoted the upper end of a grappling dog. At the lower part of their side edges, the grappling dogs are provided with outwardly projecting shoulders for engaging the lower end of the cylindrical liner. Extending through the ring-like threaded portion is an operating bolt, the lower end of which has a disk. The confronting edges of the grappling dogs are curved inwardly towards each other and the edges are adapted for engagement with the disc. The bolt is turned to move the disk into the wide part of the space between the confronting edges of the grappling dogs to collapse the dogs so that they may be inserted through the liner. The liner removing tool is thrust through the liner until the projecting shoulders on the dogs pass beyond the inner end of the liner. When the bolt is turned in the opposite direction, the bolt moves the disk to a narrower space between the confronting edges of the grappling dogs to force the dogs to move outwardly. But if the liner cannot be removed, turning the bolt may not move the disk back to the wide part of the space between the confronting edges of the grappling dogs because once the tool is loosened from the liner, the ring-like threaded portion may rotate freely with the rotation of the bolt so that the bolt and disk do not move further relative to the dogs. Thus, the grappling dogs may not collapse inwardly, thereby preventing the liner removing tool from being removed.
Thus there has been a long-felt need for a simple valve seat removing tool that is capable of removing tightly wedged valve seats, but that can also be released if the valve seat cannot be removed from the pump body.